@KTS915

You can scale SVG images without loss. But not the other images like GIF, JPG or PNG for example. Many people by mistake use their largest images in themes instead of thumbnails where thumbnails normally make sense. Other people try to scale up thumbs to full size images. If you make use of large images where it is not recommended to use them you are wasting a lot of bandwidth and slow down the performance of your website very much. Try to use a thumbnail to be shown in full size and you will see that it looks terrible. So the trick is NOT to use the standard image and scale it up and down with HTML or CSS technics (only) but try to serve a perfect matching image that has not to be scaled very much.

When it comes to high density displays, e.g. on MacBooks (2560 x 1600 Pixel) or on all kinds of new mobile devices (e.g. 1,5x, 2.0x, ...) the little horror show begins. Just think about a photographers photo gallery. Do you expect the photographer to know what he is doing when he uploads his 20 or even 40 Megapixel photoshooting results? Do you expect him to show (compressed or up-)scaled results or perfectly scaled and sharpened photos?

Try to scale any photo or an image from 400x600 to 1200x1800 pixels and tell me if you like it. As you can see it is hard to find the perfect mix between high quality and high speed.

But - did you always try to see 4k TV on a small screen? It does not work. I mean, you can not see the difference between HD and Ultra HD. That`s why I think things can simply be 'overdone' for smartphones (with connection speeds you can never trust). We will see how the web evolves.

In other words: You can ignore the things around you and stay with old solutions or try to improve it a bit. I think it is not very helpful to compare a simple slider plugin solution with answers to new web challenges and theme development aspects.

I just tried to explain my view on the things. I think, responsive is for beginners, adaptive is more for professionals, but not easy to use today as you have no control over the speed issues. I mean - people understand WWW as 'world wide web', not 'world wide wait', although they are using smartphones more and more. ;-)